There is a public service advertisement on TV and radio at the moment that is confusing me. The advert aims to get more people to wear seatbelts when driving. To encourage the use of seatbelts the advert highlights that, in the reconstructed accident, it is not the impact of the driver's head on the windscreen that kills him, neither is it the impact of his ribcage on the steering wheel. The driver dies because his internal organs are not slowed down at the same speed as his body when it hits the steering wheel and the continued movement of the heart literally rips it away from the arterial vein. So we are told to wear a seatbelt.

This confuses me because I don't see how wearing a seatbelt would help in this case. The driver and car are moving at the same speed before the crash. At the moment of the crash the car is decelerated rapidly but, if he isn't wearing a seatbelt and is thus not secured, the driver will continue moving as before, as inertia demands. What has not happened is that the driver has not been thrown forwards. There is no extra energy pushing him forwards that causes extra stress on his body when he is decelerated by the steering wheel that would be prevented by wearing a seatbelt, he has simply continued moving at the same speed as before the impact. And whether wearing a seatbelt or not, the driver's internal organs will be moving at the speed of the car prior to impact and will continue to move at that speed until acted on by an external force.

Had the driver been wearing a seatbelt he certainly would have been restrained and held in his seat, thus not hitting the windscreen or steering wheel, but he would still have been decelerated just as much as if he had been stopped by the steering wheel when not wearing a seatbelt. It is true that the seatbelt would have prevented the head and ribcage injuries, but the crux of the advert's argument is that it is neither of these injuries that kills the driver, only the sudden deceleration of the driver's internal organs. That deceleration would surely be the same whether the driver is wearing a seatbelt or not, as the seatbelt cannot restrain a person's internal organs, only his body.

I imagine the advert is preying on people's ignorance and trying to scare them in to wearing a seatbelt, which is rather disappointing.